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A033832 Sum of odd divisors of n < sqrt(n) = sum of even divisors of n < sqrt(n). 1
1, 40, 100, 208, 928, 1044, 3904, 10692, 17444, 29524, 36652, 45980, 87604, 91044, 136808, 158652, 161564, 171028, 187068, 218652, 230044, 260608, 287868, 406812, 438124, 450492, 583110, 665684, 719550, 731850, 736648, 865444, 1045504 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

All terms except first one appear to be even. - Michel Marcus, Jul 15 2013

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..500

kaleidoscopic numbers [broken link]

MATHEMATICA

aQ[n_] := DivisorSum[n, # * (-1)^# &, # < Sqrt[n] & ] == 0; Select[Range[10^4], aQ] (* Amiram Eldar, Sep 23 2019 *)

PROG

(PARI) isok(n) = {so = 0; se = 0; fordiv (n, d, if (d < sqrt(n), if (d % 2, so += d, se += d))); return (so == se); } \\ Michel Marcus, Jul 14 2013

CROSSREFS

Cf. A070039, A113184.

Sequence in context: A092889 A235280 A235271 * A235017 A043219 A039396

Adjacent sequences:  A033829 A033830 A033831 * A033833 A033834 A033835

KEYWORD

easy,nonn

AUTHOR

Naohiro Nomoto

EXTENSIONS

Prepended a(1)=1, Michel Marcus, Jul 15 2013

STATUS

approved

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Last modified October 4 04:26 EDT 2022. Contains 357237 sequences. (Running on oeis4.)